Versatile full-colour nanopainting enabled by a pixelated plasmonic metasurface

Wafer-Scale Replication of Plasmonic Nanostructures via Microbubbles for Nanophotonics

Quasi-3D plasmonic nanostructures are in high demand for their ability to manipulate and enhance light-matter interactions at subwavelength scales, making them promising building blocks for diverse nanophotonic devices. Despite their potential, the integration of these nanostructures with optical sensors and imaging systems on a large scale poses challenges. Here, a robust technique for the rapid, scalable, and seamless replication of quasi-3D plasmonic nanostructures is presented straight from their production wafers using a microbubble process. This approach not only simplifies the integration of quasi-3D plasmonic nanostructures into a wide range of standard and custom optical imaging devices and sensors but also significantly enhances their imaging and sensing performance beyond the limits of conventional methods. This study encompasses experimental, computational, and theoretical investigations, and it fully elucidates the operational mechanism. Additionally, it explores a versatile set of options for outfitting nanophotonic devices with custom-designed plasmonic nanostructures, thereby fulfilling specific operational criteria.

Directional Phase and Polarization Manipulation Using Janus Metasurfaces

Janus metasurfaces, exemplifying two-faced 2D metamaterials, have shown unprecedented capabilities in asymmetrically manipulating the wavefront of electromagnetic waves in both forward and backward propagating directions, enabling novel applications in asymmetric information processing, security, and signal multiplexing. However, current Janus metasurfaces only allow for directional phase manipulation, hindering their broader application potential. Here, the study proposes a versatile Janus metasurface platform that can directionally control the phase and polarization of terahertz waves by integrating functionalities of half-wave plates, quarter-wave plates, and metallic gratings within a cascaded metasurface structure. As a proof-of-principle, the study experimentally demonstrates Janus metasurfaces capable of independent and simultaneous control over phase and polarization, showcasing propagation direction-encoded focusing and polarization conversion. Moreover, the directionally focused points are utilized with distinct polarization states for advanced applications in direction- and polarization-sensitive detection and imaging. This unique strategy for simultaneous phase and polarization control with direction-dependent versatility opens new avenues for designing ultra-compact devices with significant implications in imaging, encryption, and data storage.

Ultrafast Metaphotonic PCR Chip with Near-Perfect Absorber

Polymerase chain reaction (PCR) is the gold standard for nucleic acid amplification and quantification in diverse fields such as life sciences, global health, medicine, agricultural science, forensic science, and environmental science for global sustainability. However, implementing a cost-effective PCR remains challenging for rapid preventive medical action to the widespread pandemic diseases due to the absence of highly efficient and low-cost PCR chip-based POC molecular diagnostics. Here, this work reports an ultrafast metaphotonic PCR chip as a solution of a cost-effective and low-power-consumption POC device for the emerging global challenge of sustainable healthcare. This work designs a near-perfect photonic meta-absorber using ring-shaped titanium nitride to maximize the photothermal effect and realize rapid heating and cooling cycles during the PCR process. This work fabricates a large-area photonic meta-absorber on a 6-inch wafer cost-effectively using simple colloidal lithography. In addition, this work demonstrates 30 thermocycles from 65 (annealing temperature) to 95 °C (denaturation temperature) within 3 min 15 s, achieving an average 16.66 °C s-1 heating rate and 7.77 °C s-1 cooling rate during thermocycling, succeeding rapid metaphotonic PCR. This work believes a metaphotonic PCR chip can be used to create a low-cost, ultrafast molecular diagnostic chip with a meta-absorber.

Chemically and geometrically programmable photoreactive polymers for transformational humidity-sensitive full-color devices

Humidity-sensitive structural color has emerged as a promising technology due to its numerous advantages that include fast response, intuitiveness, stand-alone capability, non-toxicity, as well as resistance to thermal and chemical stresses. Despite immense technological advancements, these structural colors lack the ability to present independent multiple images through transformation. Herein, we present an approach to address this constraint by introducing a chemically and geometrically programmable photoreactive polymer which allows preparation of transformational humidity-sensitive full-color devices. Utilizing azido-grafted carboxymethyl cellulose (CMC-N3) allows adjustments in swelling properties based on the grafting ratio (Γ) of azido groups upon UV-induced crosslinking. Also, the distinctive photo-curability of the polymer enables precise geometric control to achieve vivid colors in combination with disordered plasmonic cavities. Our work culminates in the development of an advanced anti-counterfeiting multiplexer capable of displaying different full-color images with variation in humidity levels. The showcased color displays signify pivotal breakthroughs in tunable optical technologies, illustrating how chemical modifications in hydrogels provides additional degrees of freedom in the design of advanced optical devices.

Multidimensional Encryption by Chip-Integrated Metasurfaces

Facing the challenge of information security in the current era of information technology, optical encryption based on metasurfaces presents a promising solution to this issue. However, most metasurface-based encryption techniques rely on limited decoding keys and struggle to achieve multidimensional complex encryption. It hinders the progress of optical storage capacity and puts encryption security at a disclosing risk. Here, we propose and experimentally demonstrate a multidimensional encryption system based on chip-integrated metasurfaces that successfully incorporates the simultaneous manipulation of three-dimensional optical parameters, including wavelength, direction, and polarization. Hence, up to eight-channel augmented reality (AR) holograms are concealed by near- and far-field fused encryption, which can only be extracted by correctly providing the three-dimensional decoding keys and then vividly exhibit to the authorizer with low crosstalk, high definition, and no zero-order speckle noise. We envision that the miniature chip-integrated metasurface strategy for multidimensional encryption functionalities promises a feasible route toward the encryption capacity and information security enhancement of the anticounterfeiting performance and optically cryptographic storage.

7D High-Dynamic Spin-Multiplexing

Multiplexing technology creates several orthogonal data channels and dimensions for high-density information encoding and is irreplaceable in large-capacity information storage, and communication, etc. The multiplexing dimensions are constructed by light attributes and spatial dimensions. However, limited by the degree of freedom of interaction between light and material structure parameters, the multiplexing dimension exploitation method is still confused. Herein, a 7D Spin-multiplexing technique is proposed. Spin structures with four independent attributes (color center type, spin axis, spatial distribution, and dipole direction) are constructed as coding basic units. Based on the four independent spin physical effects, the corresponding photoluminescence wavelength, magnetic field, microwave, and polarization are created into four orthogonal multiplexing dimensions. Combined with the 3D of space, a 7D multiplexing method is established, which possesses the highest dimension number compared with 6 dimensions in the previous study. The basic spin unit is prepared by a self-developed laser-induced manufacturing process. The free state information of spin is read out by four physical quantities. Based on the multiple dimensions, the information is highly dynamically multiplexed to enhance information storage efficiency. Moreover, the high-dynamic in situ image encryption/marking is demonstrated. It implies a new paradigm for ultra-high-capacity storage and real-time encryption.

Operando Colorations from Real-Time Growth of 3D-Printed Nanoarchitectures

While artificial 3D nanostructures can generate precise and flexible coloration, their real-time color changes during 3D nanoprinting remain unexplored owing to the inherent challenges of in situ transient measurements and observations. In this study, a 3D-printing system which supports the operando observation/measurement of the color dynamics of subwavelength metallic nanoarchitectures fabricated in real time is developed and evaluated. During 3D printing, the dimensions and geometries of the 3D nanostructures grow over time, producing a large library of optical spectra associated with real-time color changes. Only a timer is needed to define the expected colors from a single 3D print run. Fin-like nanostructures are used to toggle colors based on the polarization effect and produce color gradients. Based on structural coloration, nanoarchitectures are designed and printed to animate desired color patterns. Moreover, the resulting color dynamics can also serve as an operando identifier for real-time structural information during 3D nanoprinting. A single print run enables the efficient creation of a comprehensive library of desired colorations owing to the flexibility in time-dependent controllability and 3D geometries at the subwavelength scale. 3D nanoprinted plasmonic structures exhibiting time-varying colorations (4D printing of colors) uniquely redefines the coloring stategy, offering considerable potential for numerous applications.

Dynamic Hyperspectral Holography Enabled by Inverse-Designed Metasurfaces with Oblique Helicoidal Cholesterics

Metasurfaces are flat arrays of nanostructures that allow exquisite control of phase and amplitude of incident light. Although metasurfaces offer new active element for both fundamental science and applications, the challenge still remains to overcome their low information capacity and passive nature. Here, by integrating an inverse-designed-metasurface with oblique helicoidal cholesteric liquid crystal (ChOH), simultaneous spatial and spectral tunable metasurfaces with a high information capacity for dynamic hyperspectral holography, are demonstrated. The inverse design facilitates a single-phase map encoding of ten independent holographic images at different wavelengths. ChOH provides precise spectral modulation with narrow bandwidth and wide tunable regime in response to programmed stimuli, thus enabling dynamic switching of the multicolor holography. The results provide simple and generalizable principles for the rational design of interactive metasurfaces that will find numerous applications, including security platform.

Single-step fabrication of liquid gallium nanoparticles via capillary interaction for dynamic structural colours

Incorporating structural coloured materials in flexible and stretchable elastomeric substrates requires numerous steps that compromise their scalability and economic viability for prospective applications in visual sensors and displays. Here we describe a one-step approach for fabricating plasmonic Ga nanostructures embedded in a polydimethylsiloxane substrate exhibiting tunable chromaticity, in response to mechanical stimuli. The process exploits the capillary interactions between uncrosslinked oligomeric chains of the substrate and Ga metal deposited by thermal evaporation, as elucidated by a theoretical model that we developed. By tuning the oligomer content in polydimethylsiloxane, we attain a range of colours covering a substantial gamut in CIE (Commission Internationale de l'Éclairage) coordinates. This mechanochromic flexible substrate shows reversible response to external mechanical stimuli for ~80,000 cycles. We showcase the capabilities of our processing technique by presenting prototypes of reflective displays and sensors for monitoring body parts, smart bandages and the capacity of the nanostructured film to map force in real time.

Tailoring high-refractive-index nanocomposites for manufacturing of ultraviolet metasurfaces

Nanoimprint lithography (NIL) has been utilized to address the manufacturing challenges of high cost and low throughput for optical metasurfaces. To overcome the limitations inherent in conventional imprint resins characterized by a low refractive index (n), high-n nanocomposites have been introduced to directly serve as meta-atoms. However, comprehensive research on these nanocomposites is notably lacking. In this study, we focus on the composition of high-n zirconium dioxide (ZrO2) nanoparticle (NP) concentration and solvents used to produce ultraviolet (UV) metaholograms and quantify the transfer fidelity by the measured conversion efficiency. The utilization of 80 wt% ZrO2 NPs in MIBK, MEK, and acetone results in conversion efficiencies of 62.3%, 51.4%, and 61.5%, respectively, at a wavelength of 325 nm. The analysis of the solvent composition and NP concentration can further enhance the manufacturing capabilities of high-n nanocomposites in NIL, enabling potential practical use of optical metasurfaces.

A water-soluble label for food products prevents packaging waste and counterfeiting

Sustainability, humidity sensing and product origin are important features of food packaging. While waste generated from labelling and packaging causes environmental destruction, humidity can result in food spoilage during delivery and counterfeit-prone labelling undermines consumer trust. Here we introduce a food label based on a water-soluble nanocomposite ink with a high refractive index that addresses these issues. By patterning the nanocomposite ink using nanoimprint lithography, the resultant metasurface shows bright and vivid structural colours. This method makes it possible to quickly and inexpensively create patterns on large surfaces. A QR code is also developed that can provide up-to-date information on food products. Microprinting hidden in the QR code protects against counterfeiting, cannot be physically detached or replicated and may be used as a humidity indicator. Our proposed food label can reduce waste while ensuring customers receive accurate product information.

Intracavity spatially modulated metasurfaces for a wavelength-tunable figure-9 vortex fiber laser

Intracavity optical metasurfaces with compact and flexible light manipulation capabilities, effectively enrich the implementation of miniaturized and user-friendly orbital angular momentum (OAM) laser sources. Here we demonstrate a wavelength-tunable figure-9 Yb-doped vortex fiber laser solely with standard non-polarization-maintaining single-mode fibers, which utilizes a gap-surface plasmon (GSP) metasurface as the intracavity mode regulation component to generate OAM beams, extending the avenues and related applications for cost-effective OAM laser sources. Gained by the broadband operation range of the metasurface, the figure-9 fiber laser could emit OAM light with center wavelength tunable from 1020 nm to 1060 nm and of high mode purity (about 90%). OAM beams with different topological charges such as l = ±1 have been obtained by changing the metasurface design. The proposed fiber laser with the intracavity GSP metasurface provides a reliable and customized output of OAM beams at the laser source, holding great promise for a wide range of applications in optical communications, sensing, and super-resolution imaging.

Two-dimensional transmissive structural colors for high-security information encryption

Structural colors produced from nanostructures have attracted much attention due to their promising advantages of long-term stability and high resolution. Many nanostructures like metasurfaces have been demonstrated to generate color information in the transmission or reflection mode. Here, a strategy of combining polarization-insensitive and polarization-sensitive transmissive structural color is proposed to realize convenient and diverse encrypted pattern designs. A two-dimensional metasurface, whose polarization characteristics are determined by the size of a nanobrick unit, is embedded inside an optical cavity to produce transmissive structural color. The polarization-insensitive transmissive structural color exhibits a wide color gamut and high excitation purity in all polarization states, while the polarization-sensitive transmissive structural color maintains the similar color appearance in x-direction polarization but appears nearly black in y-direction polarization. Combining these two transmissive structural colors can achieve diverse images designed at different polarizations instead of simply hiding the image in a specific polarization state. An image of "flower and flowerpot" using the generated colors is visually illustrated, which shows that the proposed transmissive structural colors would have great potential in the areas of security information encryption.

Switchable Two-Dimensional AND and Exclusive OR Operation Based on Dual-Wavelength Metasurfaces

Logic operation serves as the foundation and core element of computing networks; it will bring huge vitality to advanced information processing with its adaptation in the optical domain. As fundamental logic operations, AND and exclusive OR (XOR) operations serve a multitude of purposes, such as their ability to cooperate in enabling image processing and interpretation. Here, we propose and experimentally demonstrate a wavelength multiplexed AND and XOR function based on metasurfaces. By combining two cosine gratings with distinct frequencies and an initial phase difference of π/2, we extract the similarities and differences between two input images simultaneously by illuminating them with 445 and 633 nm wavelengths. Additionally, we explore its potential in information encryption, where overall security is enhanced by distributing distinct parts of initial information and encoded keys to different receivers. This design possesses the benefits of convenient mode switching and high-quality imaging, facilitating advanced applications in pattern recognition, machine vision, medical diagnosis, etc.

Electrophoretic Deposition of Single Nanoparticles

The controlled assembly of colloid particles on a solid substrate has always been a major challenge in colloid and surface science. Here we provide an overview of electrophoretic deposition (EPD) of single charge-stabilized nanoparticles. We demonstrate that surface templated EPD (STEPD) assembly, which combines EPD with top-down nanofabrication, allows a wide range of nanoparticles to be built up into arbitrary structures with high speed, scalability, and excellent fidelity. We will also discuss some of the current colloid chemical limitations and challenges in STEPD assembly for sub-10 nm nanoparticles and for the fabrication of densely packed single particle arrays.

Switchable unidirectional emissions from hydrogel gratings with integrated carbon quantum dots

Directional emission of photoluminescence despite its incoherence is an attractive technique for light-emitting fields and nanophotonics. Optical metasurfaces provide a promising route for wavefront engineering at the subwavelength scale, enabling the feasibility of unidirectional emission. However, current directional emission strategies are mostly based on static metasurfaces, and it remains a challenge to achieve unidirectional emissions tuning with high performance. Here, we demonstrate quantum dots-hydrogel integrated gratings for actively switchable unidirectional emission with simultaneously a narrow divergence angle less than 1.5° and a large diffraction angle greater than 45°. We further demonstrate that the grating efficiency alteration leads to a more than 7-fold tuning of emission intensity at diffraction order due to the variation of hydrogel morphology subject to change in ambient humidity. Our proposed switchable emission strategy can promote technologies of active light-emitting devices for radiation control and optical imaging.

Metalens for Accelerated Optoelectronic Edge Detection under Ambient Illumination

Analog systems may allow image processing, such as edge detection, with low computational power. However, most demonstrated analog systems, based on either conventional 4-f imaging systems or nanophotonic structures, rely on coherent laser sources for illumination, which significantly restricts their use in routine imaging tasks with ambient, incoherent illumination. Here, we demonstrated a metalens-assisted imaging system that can allow optoelectronic edge detection under ambient illumination conditions. The metalens was designed to generate polarization-dependent optical transfer functions (OTFs), resulting in a synthetic OTF with an isotropic high-pass frequency response after digital subtraction. We integrated the polarization-multiplexed metalens with a polarization camera and experimentally demonstrated single-shot edge detection of indoor and outdoor scenes, including a flying airplane, under ambient sunlight illumination. The proposed system showcased the potential of using polarization multiplexing for the construction of complex optical convolution kernels toward accelerated machine vision tasks such as object detection and classification under ambient illumination.

Micro- and nanofabrication of dynamic hydrogels with multichannel information

Creating micro/nanostructures containing multi-channel information within responsive hydrogels presents exciting opportunities for dynamically changing functionalities. However, fabricating these structures is immensely challenging due to the soft and dynamic nature of hydrogels, often resulting in unintended structural deformations or destruction. Here, we demonstrate that dehydrated hydrogels, treated by a programmable femtosecond laser, can allow for a robust fabrication of micro/nanostructures. The dehydration enhances the rigidity of the hydrogels and temporarily locks the dynamic behaviours, significantly promoting their structural integrity during the fabrication process. By utilizing versatile dosage domains of the femtosecond laser, we create micro-grooves on the hydrogel surface through the use of a high-dosage mode, while also altering the fluorescent intensity within the rest of the non-ablated areas via a low-dosage laser. In this way, we rationally design a pixel unit containing three-channel information: structural color, polarization state, and fluorescent intensity, and encode three complex image information sets into these channels. Distinct images at the same location were simultaneously printed onto the hydrogel, which can be observed individually under different imaging modes without cross-talk. Notably, the recovered dynamic responsiveness of the hydrogel enables a multi-information-encoded surface that can sequentially display different information as the temperature changes.

Dynamic Spectral Modulation Enabled by Conductive Polymer-Integrated Plasmonic Nanodisk-Hole Arrays

The electrically driven optical performance modulation of the plasmonic nanostructure by conductive polymers provides a prospective technology for miniaturized and integrated active optoelectronic devices. These features of wafer-scale and flexible preparation, a wide spectrum adjustment range, and excellent electric cycling stability are critical to the practical applications of dynamic plasmonic components. Herein, we have demonstrated a large-scale and flexible active plasmonic nanostructure constructed by electrochemically synthesizing nanometric-thickness conductive polymer onto spatially mismatched Au nanodisk-hole (AuND-H) array on the poly(ethylene terephthalate) (PET) substrate, offering low-power electrically driven switching of reflective light in a wide wavelength range of 550-850 nm. The composite structure of the polymer/AuND-H array supports multiple plasmonic resonance modes with strong near-field enhancement and confinement, which provides an excellent dynamic spectral modulation platform. As a result, the PPy/AuND-H array achieves 18.4% reversible switching of spectral intensity at 780 nm and speedy response time, as well as maintains a stable dynamic modulation range at two-potential cycling between -0.6 and 0.1 V after 200 modulation cycles. Compared to the case of the PPy/AuND-H array, the PANI/AuND-H array obtains a more extensive intensity modulation of 25.1% at 750 nm, which is attributed to the significant differences in the extinction coefficient between the oxidized and reduced states of PANI, but its modulation range degrades apparently after 20 cycles driven at applied voltages between -0.1 and 0.8 V. Additionally, the cycling stability could be further improved by reducing the modulation voltage range. Our proposed electromodulated composite structure provides a promising technological proposal for dynamically plasmonic reconfigurable devices.

Perovskite single-pixel detector for dual-color metasurface imaging recognition in complex environment

Highly efficient multi-dimensional data storage and extraction are two primary ends for the design and fabrication of emerging optical materials. Although metasurfaces show great potential in information storage due to their modulation for different degrees of freedom of light, a compact and efficient detector for relevant multi-dimensional data retrieval is still a challenge, especially in complex environments. Here, we demonstrate a multi-dimensional image storage and retrieval process by using a dual-color metasurface and a double-layer integrated perovskite single-pixel detector (DIP-SPD). Benefitting from the photoelectric response characteristics of the FAPbBr2.4I0.6 and FAPbI3 films and their stacked structure, our filter-free DIP-SPD can accurately reconstruct different colorful images stored in a metasurface within a single-round measurement, even in complex environments with scattering media or strong background noise. Our work not only provides a compact, filter-free, and noise-robust detector for colorful image extraction in a metasurface, but also paves the way for color imaging application of perovskite-like bandgap tunable materials.

Longitudinally variable 3D optical polarization structures

Generation and manipulation of three-dimensional (3D) optical polarization structures have received considerable interest because of their distinctive optical features and potential applications. However, the realization of multiple 3D polarization structures in a queue along the light propagation direction has not yet been reported. We propose and experimentally demonstrate a metalens to create longitudinally variable 3D polarization knots. A single metalens can simultaneously generate three distinct 3D polarization knots, which are indirectly validated with a rotating polarizer. The 3D polarization profiles are dynamically modulated by manipulating the linear polarization direction of the incident light. We further showcase the 3D image steganography with the generated 3D polarization structures. The ultrathin nature of metasurfaces and unique properties of the developed metalenses hold promise for lightweight polarization systems applicable to areas such as 3D image steganography and virtual reality.

Mid-Infrared Gas Sensing Based on Electromagnetically Induced Transparency in Coupled Plasmonic Resonators

The existence of surface plasmon polaritons in doped silicon micro-scale structures has opened up new and innovative possibilities for applications, such as sensing, imaging, and photonics. A CMOS-compatible doped Si plasmonic sensor is proposed and investigated. The plasmon resonance can be tuned by controlling the carrier density and dopant concentration. In this paper, we demonstrate that using silicon doped with phosphorus at a concentration of 5 × 1020 cm-3 can induce surface plasmon resonance in the mid-infrared region. Two ring resonators of two different radii based on metal-insulator-metal waveguide structures are studied individually. Then, the two ring resonators are integrated in the same device. When the two ring resonators are coupled and resonate at the same frequency; two distinct resonance spectral lines are generated with striking features that improve its potential use for sensing and modulation applications. The propagating plasmonic mode is studied, including its mode profile and bend loss. We evaluate the effectiveness of a microstructure gas sensor with dimensions of 15 μm × 15 μm by measuring its sensitivity and selectivity towards methane and ethane gases. Small alterations in the surrounding refractive index led to noticeable shifts in the resonance peak. The sensor achieved a sensitivity of 7539.9 nm/RIU at the mid-infrared spectral range around the 7.7 μm wavelength. Furthermore, by combining the resonators, we can achieve a smaller full width at half maximum (FWHM), which will ultimately result in greater sensitivity than using a single-ring resonator or other plasmonic resonator configurations. Once the sensitivity and selectivity of the sensor are measured, the FOM can be calculated by dividing the sensitivity by the selectivity of the sensor, resulting in an FOM of 6732.

Large area structural color printing based on dot-matrix laser interference patterning

Optically Variable Devices (OVDs) are widely used as security features in anti-counterfeiting efforts. OVDs enable the display of color dynamic effects that are easily interpreted by the user. However, obtaining these elements over large areas poses certain challenges in terms of efficiency. The paper presents a modified approach for manufacturing plasmonic type OVDs through dot-matrix technology, which is a standard origination step of security holograms. By adjusting the spatial filters in the optical scheme, it is possible to double the resolution of the recorded quasi-sinusoidal diffraction gratings. The experiments confirm the creation of diffraction gratings with frequencies from 1600 to 3500 lines per mm, which facilitates the production of plasmonic zero-order spectral filters. The paper shows how the transmission characteristics of the studied elements are affected by the geometric parameters of the diffraction grating, silver layer thickness, angle of incidence, and polarization of light. The results have shown that using the proposed method it is possible to obtain 1D or 2D structural color OVD-image on a large area - several square centimeters and more. High speed recording of such elements is provided: the exposure time was from 120 to 400 ms depending on the grating resolution for a 0.05 mm2 frame, the total printing time for the size of the 25×25 mm2 OVD was about 2.5 hours for a 1D element, and less than 3.5 hours for a 2D element. Thus, the proposed method and the OVD elements produced by it can be useful to designers of optical security elements as a simpler and faster alternative to electron-beam lithographic technologies.

Processable circularly polarized luminescence material enables flexible stereoscopic 3D imaging

Endowing three-dimensional (3D) displays with flexibility drives innovation in the next-generation wearable and smart electronic technology. Printing circularly polarized luminescence (CPL) materials on stretchable panels gives the chance to build desired flexible stereoscopic displays: CPL provides unusual optical rotation characteristics to achieve the considerable contrast ratio and wide viewing angle. However, the lack of printable, intense circularly polarized optical materials suitable for flexible processing hinders the implementation of flexible 3D devices. Here, we report a controllable and macroscopic production of printable CPL-active photonic paints using a designed confining helical co-assembly strategy, achieving a maximum luminescence dissymmetry factor (glum) value of 1.6. We print customized graphics and meter-long luminous coatings with these paints on a range of substates such as polypropylene, cotton fabric, and polyester fabric. We then demonstrate a flexible textile 3D display panel with two printed sets of pixel arrays based on the orthogonal CPL emission, which lays an efficient framework for future intelligent displays and clothing.

A Canvas of Spatially Arranged DNA Strands that Can Produce 24-bit Color Depth

Nucleic acid microarray photolithography combines density, throughput, and positional control in DNA synthesis. These surface-bound sequence libraries are conventionally used in large-scale hybridization assays against fluorescently labeled, perfect-match DNA strands. Here, we introduce another layer of control for in situ microarray synthesis─hybridization affinity─to precisely modulate fluorescence intensity upon duplex formation. Using a combination of Cy3-, Cy5-, and fluorescein-labeled targets and an ensemble of truncated DNA probes, we organize 256 shades of red, green, and blue intensities that can be superimposed and merged. In so doing, hybridization alone is able to produce a large palette of 16 million colors or 24-bit color depth. Digital images can be reproduced with high fidelity at the micrometer scale by using a simple process that assigns sequence to any RGB value. Largely automated, this approach can be seen as miniaturized DNA-based painting.

Functionalizing nanophotonic structures with 2D van der Waals materials

The integration of two-dimensional (2D) van der Waals materials with nanostructures has triggered a wide spectrum of optical and optoelectronic applications. Photonic structures of conventional materials typically lack efficient reconfigurability or multifunctionality. Atomically thin 2D materials can thus generate new functionality and reconfigurability for a well-established library of photonic structures such as integrated waveguides, optical fibers, photonic crystals, and metasurfaces, to name a few. Meanwhile, the interaction between light and van der Waals materials can be drastically enhanced as well by leveraging micro-cavities or resonators with high optical confinement. The unique van der Waals surfaces of the 2D materials enable handiness in transfer and mixing with various prefabricated photonic templates with high degrees of freedom, functionalizing as the optical gain, modulation, sensing, or plasmonic media for diverse applications. Here, we review recent advances in synergizing 2D materials to nanophotonic structures for prototyping novel functionality or performance enhancements. Challenges in scalable 2D materials preparations and transfer, as well as emerging opportunities in integrating van der Waals building blocks beyond 2D materials are also discussed.

Dielectric Metasurface for Synchronously Spiral Phase Contrast and Bright-Field Imaging

Spiral phase contrast imaging and bright-field imaging are two widely used modes in microscopy, providing distinct morphological information about objects. However, conventional microscopes are always unable to operate with these two modes at the same time and need additional optical elements to switch between them. Here, we present a microscopy setup that incorporates a dielectric metasurface capable of achieving spiral phase contrast imaging and bright-field imaging synchronously. The metasurface not only can focus the light for diffraction-limited imaging but also can perform a two-dimensional spatial differentiation operation by imparting an orbital angular momentum to the incident light field. This allows two spatially separated images to be simultaneously obtained, one containing high-frequency edge information and the other showing the entirety of the object. Combined with the advantages of planar architecture and ultrathin thickness of the metasurface, this approach is expected to provide support in the fields of microscopy, biomedicine, and materials science.

Tailoring Iridescent Visual Appearance with Disordered Resonant Metasurfaces

The nanostructures of natural species offer beautiful visual appearances with saturated and iridescent colors, and the question arises whether we can reproduce or even create unique appearances with man-made metasurfaces. However, harnessing the specular and diffuse light scattered by disordered metasurfaces to create attractive and prescribed visual effects is currently inaccessible. Here, we present an interpretive, intuitive, and accurate modal-based tool that unveils the main physical mechanisms and features defining the appearance of colloidal disordered monolayers of resonant meta-atoms deposited on a reflective substrate. The model shows that the combination of plasmonic and Fabry-Perot resonances offers uncommon iridescent visual appearances, differing from those classically observed with natural nanostructures or thin-film interferences. We highlight an unusual visual effect exhibiting only two distinct colors and theoretically investigate its origin. The approach can be useful in the design of visual appearance with easy-to-make and universal building blocks having a large resilience to fabrication imperfections and potential for innovative coatings and fine-art applications.